Technical advances in creating high-density and large memory capacity magneto-optical disks whereon recorded information can be re-written are attracting considerable attention. In particular, research aimed at improving the transfer rate of data in magneto-optical disks capable of overwrite (wherein erasing operation is unnecessary) is being viewed with interest. As a method of recording information onto magneto-optical disks based on the overwrite method, using a magnetic field modulation flying head is regarded as the most effective method. In this method, a magnetic head is attached to a slider and the slider glides above a magneto-optical disk due to high rotation speed of the magneto-optical disk. Recording is carried out on the magneto-optical disk by modulation of a magnetic field generated by the magnetic head (see T. Nakao, M. Ojima, T. Miyamura, S. Okamine, H. Sukeda, N. Ohta and Y. Takeuchi, Jpn. J. Appl. Phys., Vol. 26, (1987) Suppl. 26-4, pp. 147-154).
In a flying head, a floating gap between the magnetic head and the magneto-optical disk is kept constant by dynamically balancing a floating force with a depressing force. The floating force is the force exerted upwards on the slider due to an air flow between the magneto-optical disk and the slider bearing the magnetic head. The depressing force is the force exerted downwards on the slider by a supporting mechanism that holds the slider.
However, the floating gap changes substantially due to changes in the rotation speed of the magneto-optical disk or due to changes in the depressing force exerted by the supporting mechanism. For example, when the magneto-optical disk is rotated at a constant high velocity in CAV (Constant Angular Velocity) mode, linear velocity varies depending on a radial position on the magneto-optical disk. If the depressing force exerted on the magnetic head is constant, the floating gap changes depending on the radial position, i.e., the floating gap becomes progressively smaller as the slider approaches the inner section of the magneto-optical disk. Further, in the case where a substrate of the magneto-optical disk is made of plastic, the floating gap changes due to warping or undulation of the substrate since the magnetic head does not follow the warping or undulation.
When the floating gap changes, the intensity of the magnetic field applied to a recording film of the magneto-optical disk by the magnetic head also changes. As a result, when the applied magnetic field is too weak, information cannot be recorded in a desired recording area with certainty (unsaturated recording). On the other hand, when the applied magnetic field is too strong, information also gets recorded in areas other than the desired recording area. Consequently, recorded bit shapes become uneven and signal quality of recorded signals deteriorates.
In order to resolve this problem, patent applications have been filed in the Japanese Patent and Trademark Office, such as Patent Application No. 323322/1989 (Tokuganhei 1-323322). In this patent application, a magnetic recording/reproducing device that uses a magneto-optical disk provided with ,a conductive film is disclosed. An electrode is provided on a bottom face of a slider. Electrostatic capacity between the electrode and the conductive film of the magneto-optical disk is detected. The intensity of a magnetic field generated by a magnetic head is controlled so as to keep the floating gap constant according to the detected electrostatic capacity. That is, a depressing force exerted on the slider by the magnetic head supporting mechanism, or an electric current applied to the magnetic head is controlled so as to keep the floating gap constant according to the detected electrostatic capacity. Information is thus recorded on the magneto-optical disk by controlling the intensity of the magnetic field generated by the magnetic head.
However, in the magnetic recording/reproducing device that uses the magneto-optical disk provided with the conductive film, the so-called contact-start-stop method cannot be used. In the contact-start-stop method, the magnetic head is in contact with a surface of the magneto-optical disk when rotation of the magneto-optical disk is started or stopped and this method cannot be used here because the surface of the magneto-optical disk having the conductive film is coarse and has poor lubricity and, as a result, the magnetic head adheres to the surface of the disk. As a consequence, problems arise that disk rotation does not begin and that the disk gets stuck in the device and cannot be removed.
Meanwhile, a magneto-optical disk provided with a lubricant has been disclosed in Japanese Patent Laid-Open Publication No. 98857/1988 (see Tokukaisho 63-98857). However, since the lubricant in this case is in an oily state (liquid state), adherence occurs as described above between the magnetic head and the disk, and the lubricant is scattered when the magneto-optical disk is rotated at high speed.
It is an outstanding characteristic of the magneto-optical disk that it is freely removable from and insertable into the device, and in this respect it is superior to fixed-type magnetic disks such as hard disks. However, when a rotating magneto-optical disk is stopped and an attempt made to remove it from the device, it becomes impossible to do so if the magnetic head adheres as described above to the surface of the disk. Moreover, magneto-optical disks using a lubricant in an oily state also have the problem that dust accumulates easily thereon.